The present invention relates to a pressurizing apparatus used for pressurization of a metal mold in sheet-metal presswork and clamping of a metal mold in die casting and injection molding.
As a mechanism for applying thrust to a metal mold so as to carry out pressurization of the metal mold in sheet-metal presswork and the like and clamping of the metal mold in die casting and injection molding, there are mainly the following two mechanisms. One is a motor-driven pressurizing mechanism in which a rotational motion of a motor is converted into a linear motion by a mechanism such as a screw feeding mechanism for converting a rotational motion into a linear motion and an output shaft is moved forward and rearward by the linear motion. The other is a hydraulic pressurizing mechanism in which a hydraulic pump is actuated by a rotational driving force of a motor to cause a hydraulic cylinder to directly act by oil discharged from the hydraulic pump to move an output shaft connected to the hydraulic cylinder forward and rearward.
By using any of the above mechanisms, however, it is difficult to obtain both high-speed movement and high thrust because a motor capacity is limited to a small value due to circumstances such as manufacturing cost. In other words, a carrying speed has to be reduced by reducing a speed reducing ratio of a powertrain or the like so as to obtain high-speed movement while thrust has to be reduced by increasing the speed reducing ratio of the powertrain or the like so as to obtain high thrust.
Therefore, an object of the present invention relates to a pressurizing apparatus used for pressurization of a metal mold in sheet-metal presswork and the like and clamping of a metal mold in die casting, injection molding, and the like and is to provide a low-cost pressurizing apparatus with high productivity by combining a direct-connecting mechanism for moving an output shaft with low thrust and at a high speed and a fluid pressure mechanism for driving the output shaft at a low speed and with high thrust with each other.
An invention described in claim 1 is formed of a pressurizing apparatus including a fixed portion, an input shaft for acting directly in an axial direction with respect to the fixed portion, an output shaft extending coaxially with the input shaft to slide with respect to the fixed portion and the input shaft, a direct-connecting mechanism for directly connecting the output shaft and the input shaft and for causing the input shaft to directly act with respect to the fixed portion to thereby rapidly carry the output shaft with respect to the fixed portion, a fluid pressure mechanism for connecting the input shaft and the output shaft in a fluid manner and for causing the input shaft to directly act with respect to the output shaft to thereby increase biasing of the input shaft by Pascal""s law and transmit the biasing to the output shaft, and a control mechanism actuated by biasing applied by the input shaft to control fluid connection of the input shaft and the output shaft to each other.
The pressurizing apparatus according to the invention described in claim 1 operates as follows in a step such as pressurization of a metal mold in sheet-metal presswork and clamping of a metal mold in injection molding. The present apparatus directly connects the output shaft to the input shaft to rapidly carry the output shaft in a reciprocating stroke excluding a vicinity of a turning point between going and returning of the metal mold. By this rapid carrying, it is possible to move the metal mold with the output shaft at a high speed. The present apparatus cancels direct connection and causes the input shaft to directly act with respect to the output shaft at points of a stroke in the vicinity of the turning point. Thus, the control mechanism is actuated to connect the input shaft and the output shaft to each other in a fluid manner. By this fluid connection, biasing by the input shaft can be increased by Pascal""s law and transmitted to the metal mold through the output shaft.
As a result, according to the present invention, it is possible to provide the pressurizing apparatus by which both high-speed movement of the metal mold and pressurization of the metal mold with high thrust can be obtained even if an inexpensive low-capacity motor (drive source) is used. Because it is possible to shorten processing time by moving the metal mold at a high speed, productivity is increased.
In the invention, the control mechanism for controlling fluid connection of the input shaft and the output shaft to each other is directly actuated by biasing of the input shaft applied by the input shaft. Therefore, the apparatus according to the invention does not need to have a special actuator for driving the control mechanism and can be formed with a simple structure at low cost.
An invention described in claim 2 is formed of a pressurizing apparatus according to claim 1 in which the input shaft is caused to act directly by a servomotor in the axial direction with respect to the fixed portion through a rotation/direct-action converting mechanism.
According to the invention described in claim 2, in addition to advantages of the invention described in claim 1, there are the following advantages. In other words, because the servomotor has great general versatility and it is possible to easily control switching between normal and reverse rotations, timing of switching, a rotation speed, and the like of the servomotor, it is possible to swiftly change processing conditions such as a direct-acting stroke of the output shaft and a pressurizing force without using a complicated apparatus.
An invention described in claim 3 is formed of a pressurizing apparatus according to claim 2 in which the rotation/direct-action converting mechanism is a ball screw-nut mechanism and has a ball screw supported for rotation by the fixed portion and a nut fixed to the input shaft.
According to the invention described in claim 3, in addition to advantages of the invention described in claim 2, there are the following advantages. Because the ball screw can be rotated smoothly at a high speed, it is possible to further shorten the processing time and to maintain a long life of the servomotor.
An invention described in claim 4 is formed of a pressurizing apparatus according to claims 1 to 3 in which the fluid pressure mechanism includes a first fluid chamber biased by the input shaft by causing the input shaft to directly act with respect to the output shaft and a second fluid chamber having a larger pressurizing area than the first fluid chamber to bias the output shaft and the control mechanism opens a first fluid path between the first fluid chamber and the second fluid chamber to connect the input shaft and the output shaft in a fluid manner.
According to the invention described in claim 4, in addition to advantages of the inventions described in claims 1 to 3, there are the following advantages. Because the fluid connection of the input shaft and the output shaft to each other can be carried out by only opening the first flow path by the control mechanism, it is possible to form the apparatus simply.
An invention described in claim 5 is formed of a pressurizing apparatus according to claim 4 in which the control mechanism includes a separating mechanism disposed in the first fluid path to separate the first fluid path and to cancel the separation by pressure in the first fluid chamber increased by biasing applied by the input shaft.
According to the invention described in claim 5, in addition to advantages of the invention described in claim 4, there are the following advantages. The direct-connection of the output shaft and the input shaft to each other is canceled at points of the stroke in the vicinity of the turning point between going arid returning of the metal mold and the pressure in the first fluid chamber is increased by relative sliding of both the shafts. Because the separating mechanism is actuated by this increase in pressure to open the first fluid path, it is possible to automatically shift to transmission of thrust from the input shaft to the output shaft by the fluid pressure mechanism.
An invention described in claim 6 is formed of a pressurizing apparatus according to claim 4 or 5 in which the second fluid chamber has a second fluid path communicating with a third fluid chamber provided separately from the first fluid chamber and the second fluid path is open while rapid carrying by the direct-connecting mechanism is carried out and is closed by a closing mechanism actuated by the pressure of the first fluid chamber increased by the biasing by the input shaft after direct connection by the direct-connecting mechanism is cancelled.
According to the invention described in claim 6, in addition to advantages of the invention described in claim 4 or 5, there are the following advantages. A capacity of the second fluid chamber is rapidly changed by biasing of the output shaft itself in rapid movement of the output shaft by rapid carrying. Therefore, the second fluid path through which fluid in the second fluid chamber flows in and out according to the change of the capacity is provided and connected to the third fluid chamber and the second fluid path is closed after the rapid carrying is completed to automatically shift to transmission of thrust from the input shaft to the output shaft by the fluid pressure mechanism.
An invention described in claim 7 is formed of a pressurizing apparatus according to claim 6 further including a closing mechanism for closing the second fluid path at pressure lower than pressure at which the separation by the separating mechanism is cancelled.
According to the invention described in claim 7, in addition to advantages of the invention described in claim 6, there are the following advantages. After the rapid carrying is completed, the first fluid path is opened following closing of the second fluid path and switching of operation from the rapid carrying to high-thrust pressurization is carried out automatically. Therefore, it is unnecessary to especially provide means for synchronizing operations of the direct-connecting mechanism and control mechanism and it is possible to obtain the present pressurizing apparatus at low cost and with a simple structure.
An invention described in claim 8 is formed of a pressurizing apparatus according to claim 7 in which magnets for retaining a separating member in respective positions corresponding to a separating state and a separation canceling state of the first fluid path are disposed in the control mechanism in the separating mechanism.
The invention described in claim 8 has the following advantages in addition to advantages of the invention described in claim 7. In other words, without newly providing a pressure sensor and an actuator, it is possible to maintain the separating mechanism in the separating state until internal pressure of the first fluid chamber increases to pressure at which the closing mechanism is actuated. It is also possible to maintain the separating mechanism in the separation canceling state if a pressure difference between the first fluid chamber and the second fluid chamber disappears after the separation by the separating mechanism is cancelled temporarily. Thus, it is possible to keep the first fluid path open and rearward movement of the output shaft by the fluid pressure mechanism is carried out smoothly. Therefore, it is possible to obtain the pressurizing apparatus according to the invention at low cost and with a simple structure. There is not especially a fear of trouble.
An invention described in claim 9 is formed of a pressurizing mechanism according to claims 1 to 8 in which the direct-connecting mechanism is formed by disposing an engaging member in one of the input shaft and the output shaft and disposing an engaged member in the other, direct connection of the input shaft and the output shaft to each other by the engaging member and the engaged member is maintained by biasing of the output shaft by the input shaft, and the direct connection of the input shaft and the output shaft to each other is cancelled when the biasing of the output shaft by the input shaft is attenuated.
The invention described in claim 9 has the following advantages in addition to advantages of the inventions described in claims 1 to 8. Because direct-connection of the input shaft and the output shaft to each other is maintained and cancelled by controlling biasing of the output shaft by the input shaft in the direct-connecting mechanism, is it unnecessary to provide a special actuator for driving the direct-connecting mechanism and sensors and the like and it is possible to form the apparatus at low cost and with a simple structure.
An invention described in claim 10 is formed of a pressurizing apparatus according to any one of claims 4 to 9 in which the first fluid chamber is defined by an outer peripheral portion of the input shaft, a first piston provided to the outer peripheral portion, and a first cylinder formed inside the output shaft, the second fluid chamber and the third fluid chamber are defied by an outer peripheral portion of the output shaft, a second piston provided to an axial intermediate portion of the outer peripheral portion, and a second cylinder formed inside the fixed portion and are disposed on opposite sides of the second piston in an axial direction of the output shaft.
The invention described in claim 10 has the following advantages in addition to advantages of the inventions described in claims 4 to 9. In other words, because the pressurizing apparatus according to the invention has a simple structure formed by inserting the input shaft into the output shaft formed in a tubular shape and inserting the output shaft into the fixed portion, it is possible to easily assemble the apparatus. By arranging the second fluid chamber and the third fluid chamber in the axial direction inside the second cylinder, it is possible to simply form the entire apparatus in a small size.
An invention described in claim 11 is formed of a pressurizing apparatus according to claim 10 in which the third fluid chamber has a sub-piston moved by biasing by the output shaft to absorb the biasing of the output shaft.
The invention described in claim 11 has the following advantages in addition to advantages of the invention described in claim 10. In other words, because the third fluid chamber has the sub-piston for absorbing biasing of the third fluid chamber by the output shaft, pressurization by the output shaft can be carried out without hindrance.
An invention described in claim 12 is formed of a pressurizing apparatus according to claim 10 or 11 in which the first fluid path is formed of a passage hole formed in the output shaft and connecting an outer peripheral side and an inner side of the output shaft and the second fluid path is formed of a passage hole formed in the second piston and connecting axial opposite outer faces of the second piston.
The invention described in claim 12 has the following advantages in addition to advantages of the invention described in claim 10 or 11. Because the connecting holes forming the respective fluid paths are formed as partitioning members for the respective fluid chambers, the structure is simple and can be processed easily. As compared with a case of disposing a pipe and the like outside the apparatus, resistance of fluid is smaller and there is no fear of leakage of fluid to an outside.